CHAPTER III 



ENERGY EVOLUTION OF BACTERIA, ALG^., 

 AND PLANTS 



Energy and form. Primary stages of biochemical evolution in bacteria. Evo- 

 lution of protoplasm and chromatin, the two structural components of the 

 living world. Chlorophyll and the energy of sunlight. Evolution of the 

 algje. Some physicochemical contrasts between plant and animal evo- 

 lution. 



We shall now trace some of the physicochemical principles 

 of action, reaction, and interaction as they actually appear in 

 operation in some of the simpler forms of life, beginning with 

 the bacteria. In the bacterial organisms the capture, storage, 

 release, and interaction of energy are what is best known and 

 apparently most important, while their Jorm is less known and 

 apparently less important. 



Primary Stages of Biochemical Evolution in Bacteria 



A bacterialess earth and a bacterialess ocean would soon 

 be uninhabitable either for plants or animals; conversely, it is 

 probable that bacteria-like organisms prepared both the earth 

 and the ocean for the further evolution of plants and animals, 

 and that life passed through a very long bacterial stage. 



In the origin of life bacteria appear to lie half-way be- 

 tween our hypothetical chemical precellular stages (pp. 67-71) 

 and the chemistry and definite cell structure of the lowliest 

 plants, or algae. Owing to their minute size or actual invisibil- 

 ity, bacteria are classified less by their shape than by their 

 chemical actions, reactions, and interactions, the analysis of 



which is one of the triumphs of modern research. 



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